Chromosomal data (2n = 36/37, FNa = 42-44) for samples from Burkino Faso and Senegal were reported by Gautun et al. (1985) and Volobouev and Granjon (1996); Dobigny et al. (2002b) recorded a slightly greater range in diploid and fundamental numbers in Niger samples. Rosevear (1969) included angelus in this species, but Sicard et al. (1988) discussed its possible specific status. The form nigeriae was provisionally considered valid by Rosevear (1969) but was treated as a subspecies of T. gracilis by Robbins (1974).